<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        .left{
            float: left;
            background: red;
            width: 50vw;
            height: 30vh;
            font-size: 3rem;
        }
        .right{
            float: right;
            background: blue;
            width: 50vmax;
            height: 30vh;
            font-size: 3rem;
        }

    </style>
</head>
<body>
    <div class="left">left</div>
    <div class="right">right</div>
</body>
</html>